Popping out of gear under hard braking on track

[ali_khl]

A few weeks ago I had an issue with my PH2 172, where I couldn’t down-shift into 3rd gear on the Nurbürgring during hard braking (despite heel-toe/ matching revs). I also had some knocking at some parts of the track (like the Karussell & Breidscheid), which I assume was due to me not “pulling” the engine enough while installing a new engine mount. What I had done before this session was:

1) Installed new OEM top-engine mount (Kangoo one with a bit more beef)
2) Installed new OEM Upper gearbox mount
3) Installed PhillipeM uprated dogbone
4) Changed gearbox fluid (Redline MT90)

After this experience, I decided to get some solid top-engine and upper-gearbox mounts to replace the OEM OEMs to address the knocking (Evol-Engineering ones - fantastic and without a significant increase in NVH after some mileage on them!).

During the installation, I noticed the central shaft from the spider that the upper gearbox mount slots through was loose, so I tried to tighten it up best I could, then installed the Evol mount.

I was back at the track yesterday, and the knocking and trouble downshifting to 3rd have been resolved, BUT, during very hard braking (ABS-threshold) the car now sometimes “jumps” out of 3rd into neutral, which is something I really don’t want to experience at the Ring. There are no other issues that I am experiencing with the gearbox - all gears slot-in cleanly, no crunching, tight linkage (the car is at 180k km/ 110k miles).

Does anyone any ideas? Could it be the upper gearbox mount shaft has come loose again as maybe I didn’t tighten it enough? Should I try to “pull” the engine forward away from the firewall even with the new solid top engine mount? Or is it a sign my gearbox is on its last legs…?

 

[ozclio03]

Bump I have the same issue since fitting the PMS shifter, Any help guys? Mine jumps out of 2nd but only on the most lethal late braking / weight transfer around one corner at my local track, impossible to replicate on the street!

 

[JamesBryan]

I've had the same and that's with vibratechnic uprated engine and gearbox mounts plus powerflex dogbone mount.

No idea why it happens, maybe too stiff at a guess 🤔

 

[Louis]

Bump I have the same issue since fitting the PMS shifter, Any help guys? Mine jumps out of 2nd but only on the most lethal late braking / weight transfer around one corner at my local track, impossible to replicate on the street!

Not filled the rod with sand/lead have you?

 

[bashracing]

I made a solid stainless wishbone ( no bushes ) for the hillclimb car and that sorted it, but don't use it on the road as the vibrations in the cabin were mental.

 

[Cub.]

I made a solid stainless wishbone ( no bushes ) for the hillclimb car and that sorted it, but don't use it on the road as the vibrations in the cabin were mental.

 

[bashracing]

Here's a picture from the drive home

 

[Sanj16]

Mine used to fall out of gear coming on to the Bentley straight at Snetterton just lifting through the corner before, turned out to be worn synchro in 3rd..

 

[ozclio03]

Not filled the rod with sand/lead have you?

No sand in mine yet but im tempted to for the vibrations, does sand make it more likely to pop out?

 

[ozclio03]

Mine used to fall out of gear coming on to the Bentley straight at Snetterton just lifting through the corner before, turned out to be worn synchro in 3rd..

running a rebuilt gearbox and was fine with the oem shifter. hope thats not the issue!